The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Influenza poses a heavy burden to our health service (1, 2), causing significant morbidity and mortality in older people, very young children and persons with chronic illness. Seasonal, zoonotic and pandemic influenza are constant global threats. The World Health Organization estimates that seasonal influenza causes 250,000-500,000 deaths worldwide each year. Most recently, the antigenically drifted A/Switzerland/9715293/2013 virus caused major outbreaks in various countries in Europe and North America (CDC Health Advisory regarding the potential for circulation of drifted influenza A (H3N2) viruses.(see emergency.cdc.gov/HAN/han00374.asp); Skowronski D M, Drews S J, Fonseca K, Charest H, Chambers C, Sabaiduc S, et al. Interim estimates of 2014/5 vaccine effectiveness against influenza A (H3N2) from Canada's sentinel physician surveillance network. Euro Surveill 2015; 20. Pi: 21022). Virological surveillance of influenza A(H3N2) viruses collected in the United States from Oct. 1 through Nov. 22, 2014 showed that 52% of these isolates were antigenically drifted from the A/Texas/50/2012(H3N2) vaccine virus (4). All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. Moreover avian influenza viruses such as the A(H5N1) and more recently A(H7N9), the spread of which from their regions of origin is facilitated by air travel, are often associated with a much higher mortality than traditional seasonal influenza. As such, the protective potential of immunizing formulations based on predictions of likely pathogenic strains made well in advance of actual outbreaks is necessarily limited.
One approach to addressing this problem is to increase the complexity of the vaccinating formulation. For example, co-circulation of Influenza B Yamagata and Victoria strains leading to seasonal outbreaks resulted in a call for the routine use of a quadrivalent influenza vaccine. Such an approach, however, further complicates production of seasonal influenza vaccines and does not address the fundamental issue of genetic drift from predicted strains and unanticipated introduction of new influenza strains.
Imiquimod, a synthetic toll-like receptor 7 (TLR7) agonist useful for the treatment of DNA virus infection, has been found to improve certain aspects of influenza vaccine immunogenicity in experimental animal models (Thomsen L L, Topley P, Daly M G, Brett S J, Tite J P. Imiquimod and resiquimod in a mouse model: adjuvants for DNA vaccination by particle-mediated immunotherapeutic delivery. Vaccine. 2004; 22:1799-809; Zuber A K, Bråve A, Engström G, Zuber B, Ljungberg K, Fredriksson M, et al. Topical delivery of imiquimod to a mouse model as a novel adjuvant for human immunodeficiency virus (HIV) DNA. Vaccine. 2004; 22:1791-8; Weldon W C, Zarnitsyn V G, Esser E S, Taherbhai M T, Koutsonanos D G, Vassilieva E V, et al. Effect of adjuvants on responses to skin immunization by microneedles coated with influenza subunit vaccine. PLoS One. 2012; 7:e41501; Zhang A J, Li C, To K K, Zhu H S, Lee A C, Li C G, et al. Toll-like receptor 7 agonist imiquimod in combination with influenza vaccine expedites and augments humoral immune responses against influenza A(H1N1)pdm09 virus infection in BALB/c mice. Clin Vaccine Immunol. 2014; 21:570-9). For example, treatment with topical imiquimod before intradermal trivalent influenza vaccine expedited, augmented and prolonged the immunogenicity against the immunizing influenza vaccine strains in elderly subjects with chronic illness (Hung I F, Zhang A J, To K K, Chan J F, Li C, Zhu H S, et al. Immunogenicity of intradermal trivalent influenza vaccine with topical imiquimod: a double blind randomized controlled trial. Clin Infect Dis 2014; 59:1246-55). Similar studies have noted a boost in immune response to vaccinating species as an effect of a topical TLR7 agonist, imiquimod in both human and animal models. The immunity induced was rapid and could sustain beyond the one-year period in immunosenescent elderly subjects. An imiquimod adjuvanted (i.e. mixed and injected with the vaccine formulation) vaccine has also been found to elicit higher level of IgG2a antibodies, HI titers and IFN-γ cellular response directed to immunizing species when compared to vaccine alone. Simultaneous subcutaneous administration of imiquimod as an adjuvant with DNA vaccine also enhanced the dendritic cell and Th1 lymphocyte response towards the injected antigens in mouse model (Thomsen L L, Topley P, Daly M G, Brett S J, Tite J P. Imiquimod and resiquimod in a mouse model: adjuvants for DNA vaccination by particle-mediated immunotherapeutic delivery. Vaccine. 2004; 22:1799-809; Zuber AK, Bråve A, Engström G, Zuber B, Ljungberg K, Fredriksson M, et al. Topical delivery of imiquimod to a mouse model as a novel adjuvant for human immunodeficiency virus (HIV) DNA. Vaccine. 2004; 22:1791-8). Such an increased response to vaccinated species, however, does not address issues resulting from antigenic drift or introduction of new influenza virus strains that are not present in a vaccinating formulation to a population.
Other strategies have been studied to improve the immunogenicity and breadth of the influenza vaccine by targeting the relatively conserved hemagglutinin stem, the M2 and the nucleoprotein, or by changing the mode of delivery with viral vectors. More recently, the development of self-assembling synthetic nanoparticle vaccine was also found to improve the potency and breadth of influenza virus immunity (Kanekiyo M, Wei C J, Yassine H M, McTamney P M, Boyington J C, Whittle J R, et al. Self-assembling influenza nanoparticle vaccines elicit broadly neutralizing H1N1 antibodies. Nature 2013; 499:102-6). Nevertheless, such strategies are still confined to the stage of cell-line or animal studies. The use of adjuvants including the MF59 or AS03 has demonstrated an antigen sparing effect with improved immunogenicity. Unfortunately, ] frequent local adverse events limit its utility (Montana M, Verhaeghe P, Ducros C, Terme T, Vanelle P, Rathelot P. Safety review: squalene and thimerosal in vaccines. Therapie 2010; 65:533-41; Black S, Della Cioppa G, Malfroot A, Nacci P, Nicolay U, Pellegrini M, et al. Safety of MF59-adjuvanted versus non-adjuvanted influenza vaccines in children and adolescents: an integrated analysis. Vaccine 2010; 28:7331-6). In addition the dose sparing effect is less pronounced in individuals who have been primed earlier in their lives with antigenically related viruses or vaccines. Therefore, the application of topical imiquimod pretreatment before intradermal influenza vaccination is the most simple and readily available strategy to improve and broaden the influenza vaccine immunogenicity. It has also been noted that the combination of synthetic TLR4 and TLR7 ligands can act as an adjuvant when coinjected with recombinant influenza virus hemagglutinin, and can stimulate both Th1 and Th2-type immune responses in mice, thereby providing broad neutralizing antibodies against the antigenically drifted influenza viruses (18). It is not clear, however, how effective such approaches will be in widespread immunization efforts.
Thus, there is still a need for a simple, effective, and well tolerated compositions and methods that provide an enhanced immune response and/or broadened range of effective responses to vaccine formulations